1. Field of the Invention
The present invention is a flexible hollow fiber fluid (e.g. gas) separation module optionally housed in an envelope or tube. The flexible module may be shaped (deformed, coiled or bent) into any number of desirable configurations to satisfy any number of overall system, geometry or space restrictions, specifications or limitations.
2. Description of Related Art
Hollow fiber membrane modules are commonly divided into two or three regions, wherein such regions are sealed so that fluid cannot communicate from one region to the other, except by passing the fluid through the bores of the hollow fibers or permeating the fluid across the walls of the hollow fibers. When feed fluid is introduced into the open bores, this approach is usually termed "boreside feed" or "bore feed." Alternatively, the feed fluid may contact the exterior of the hollow fibers with one or more components permeating and exiting through the hollow bores (lumen). This approach is usually termed "shellside feed" or "shell feed." Generally, a hollow fiber membrane module comprises a bundle of hollow fibers arranged in a fashion such that each end of the hollow fibers are embedded in a resin matrix commonly referred to as a tubesheet or header. Such fibers communicate through the tubesheets and are open on the opposite face of each tubesheet. The opposite face of the tubesheet means herein that face of the tubesheet which is opposite the bundle. Normally, the regions of the membrane separation module are defined and divided from one another by the tubesheets and seals about the tubesheets. In a shellside feed membrane module, the fluids to be separated are introduced into the module in the region between the tubesheets and the outside of the fibers, and the fluids which permeate through the hollow fiber membranes into the bores of the hollow fibers are removed at one or both ends of the hollow fibers in the regions adjacent to the opposite face of one or both. In shellside feed processes, the region about the hollow fiber bundles is pressurized. The non-permeating fluids are removed from a region in the area between the tubesheets but outside of the fibers. Optionally, a sweep fluid is used in the permeate side. Most commercial industrial fluid separation processes operate in this fashion.
In a boreside feed process, the mixture of fluids to be separated is introduced into one end of the membrane module adjacent to the opposite face of one of the tubesheets (i.e. the first tubesheet), such that the feed mixture flows down the bores of the hollow fibers and one or more components permeate through the walls of the hollow fibers into the region outside the fibers between the first and second tubesheets. In the region between tubesheets, the fluid which selectively permeates through the fiber membrane wall is removed from the shellside of the membrane. Those fluids which do not permeate through the membrane exit into a region adjacent to the opposite face of the second tubesheet and are removed from that region. As the tubesheets are usually comprised of a polymeric resinous material, significant bending, compressive, and sheer stresses are exerted on such tubesheets by such boreside operation. The stresses described above create a first problem with supporting the tubesheets and preventing them from collapsing in on the hollow fiber bundle.
A second problem in boreside feed is obtaining proper flow and distribution of the permeate fluid on the shell side of the fibers. One of the driving forces in a membrane separation process is a chemical potential gradient (e.g. concentration gradient or partial pressure gradient) across the membrane. As the mixture of fluids to be separated flows down the bores and the more selectively permeable fluids permeate through the hollow fibers, the concentration or partial pressure of the selectively permeable fluids along the hollow fibers is reduced and the concentration on the shellside of the selectively permeable fluids increases. This results in a lowering of the driving force.
A third problem is that if the flow of the permeate fluid on the shellside of the membranes is not properly controlled, there will be localized areas of high concentration or partial pressure of the permeate fluid and flow to the exit ports may not occur in an efficient or effective manner.
A fourth problem is the shape, geometry or volume requirements needed for conventional fluid separation modules. Conventional modules are usually in an essentially linear configuration, and thus to obtain high volumes of separation of permeate, the linear modules are often bulky, inflexible, inconvenient to position, occupy considerable space, etc. Previous attempts to change the linear shape of the module have resulted in crimping of the fibers, reduced flow, less than effective or efficient separation and the like.
A number of references which show the general state of the art include, but are not limited to, the following U.S. Pat. Nos.: 3,339,341; 3,832,830; 4,367,139; 4,451,369; 4,508,548; 4,734,106, 4,707,267; 4,781,832; 4,781,834; 4,871,379; 4,959,152; 4,961,760; 4,929,259; 5,013,331; and 5,013,437.
All patents, patent applications, references, articles, standards, and the like cited in this application are incorporated herein by reference in their entirety.
Therefore, a need exists for a fluid separation module which can be shaped (deformed) to assume a shape and size to meet space/volume requirements of the particular fluid separation application. The present invention also has weight and cost advantages as well as ease of fabrication. The present invention provides such a compact separation module and improved method of fluid separation.